JPH09129611A - Etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to ensure a high etching rate even if CO is not added to C4 F8 gas and to obtain etching characteristics, which generate little deposited substance when a silicon material layer on a substrate to be treated is etched using the C4 F8 gas. SOLUTION: When prescribed treatment gas is introduced in a treating chamber 2, which can be freely reduced in pressure therein, and plasma is generated in the chamber 2 under a reduced pressure of several m to 100mTorr or thereabouts to etch a silicon oxide material layer on a wafer W, C4 F8 gas, rate gas or O2 gas is used as the treatment gas and at the same time, the partial pressure of the C4 F8 gas is set at 0.5m to 1.5mTorr and the ratio of C4 F8 gas: O2 gas is set in a ratio of 1:1.5 to 5 to etch the silicon oxide material layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method for etching a substrate to be processed.

[0002]

2. Description of the Related Art Today, semiconductor devices are becoming highly integrated, and an etching technique for forming a contact hole of 0.3 μm with a high aspect ratio is required, and is widely used as an interlayer insulating film. Silicon oxide-based material layer, such as a silicon oxide film (Si
A technique for etching O ₂ ) with a high selectivity has become important.

The above-mentioned silicon oxide film (Si
When etching O ₂ ), an etching method is used in which an etching gas is introduced into the processing chamber and plasma is generated in the processing chamber. In this case, a so-called CxFy-based gas is generally used as an etching gas, and among them, a gas having a good x-y ratio of 1: 2 such as C ₄ F, which has a good balance between a high selection ratio and a high etching rate. _Eight gases are typical.

When the C ₄ F ₈ gas is used, conventionally, CO (carbon monoxide) gas is mixed and introduced into the processing chamber in consideration of the balance between the etching rate and the selection ratio of the base, and plasma is generated. It was generated to promote the dissociation of C ₄ F ₈ to etch the silicon oxide film (SiO ₂ ). The main etchant in this case is CF ₃ ^+, which is produced in large amounts during dissociation and becomes a depot species.
^{The +} is designed to be removed by O in the added CO.

Other typical etching gas is C
Although HF ₃ gas has been used conventionally, there is an example in which this CHF ₃ gas is also used as a mixture with CO (carbon monoxide) gas in consideration of the balance between the etching rate and the selection ratio of the base. Many.

[0006]

The above-mentioned C ₄
In the process using the F ₈ gas + CO gas, CO which is harmful to the human body is used, and therefore it is necessary to pay particular attention to handling and surroundings of the processing device. Moreover, it is a depot type C
Since a large amount of F is produced, even if it is removed with oxygen in CO as appropriate, a depot still tends to occur,
As a result, the frequency of cleaning the inside of the processing apparatus chamber was relatively high.

The present invention has been made in view of the above points, and an object thereof is to achieve a high etching rate without using CO gas and to prevent deposition of a depot in a chamber (processing chamber) of a processing apparatus. It is an object to provide a suppressed etching method.

[0008]

[Means for Solving the Problems] If CO gas is simply not used, promotion of dissociation of C ₄ F ₈ gas becomes a problem, and treatment of CF, which is a depot species, is also problematic. Therefore, in the present invention, the problem is solved by setting the partial pressure of C ₄ F ₈ gas to be lower than the conventional pressure and further adding O ₂ gas for CF removal. However, to control the dissociation of C ₄ F _8, it is necessary to control the ratio of CF ⁺ to be CF ₃ ⁺ and depot species the etchant, also the ratio of C ₄ F ₈ gas and O ₂ gas Considering.

From the above viewpoint, in order to achieve the above object,
The etching method according to claim 1, wherein a predetermined processing gas is introduced into a depressurizable processing chamber, and plasma is generated in the processing chamber under a predetermined depressurized atmosphere so that a substrate to be processed in the processing chamber is processed. In the method of etching a silicon oxide based material layer of No. ₃ , a mixed gas of C ₄ F ₈ gas, a rare gas and O ₂ is used as a processing gas, and the partial pressure of the C ₄ F ₈ gas with respect to the process pressure is 0. 5mTorr ~ 1.5mTor
The etching is performed by setting the ratio of r and C ₄ F ₈ gas: O ₂ to 1: 1.5 to 5.

The etching method according to the second aspect uses a mixed gas of CHF ₃ gas, a rare gas, and O ₂ as an etching gas, and the partial pressure of the CHF ₃ gas is 5 mTorr.
The etching is performed by setting the ratio of ₂₀ mTorr and CHF ₃ gas: O ₂ to 1: 4 to 9.

The noble gases referred to in the claims of the present application include, for example, Ar (argon) gas, He (helium) gas, Xe (xenon) gas, Kr (krypton) gas,
Ne (neon) gas is mentioned. Of course, these rare gases may be used in combination. Then, by adjusting the flow rate of each of these rare gases, C ₄ F ₈ gas and CHF ₃
It is possible to obtain a certain partial pressure for the process pressure of the gas.

According to the etching method of claim 1, C ₄
Partial pressure of F ₈ gas is 0.5 mTorr to 1.5 mTorr
Is set so that dissociation of C ₄ F ₈ is promoted, and C
_Since the ratio of ₄ F ₈ gas: O ₂ is set to 1: 1.5 to 5, the inventors of the present invention have found that C, which is an etchant.
The dissociation into F ₃ ions and CF ions that become depot species can be controlled, and the ratio of CF ₃ ions to CF ions is 1.5.
Values of up to 2.4: 1 can be obtained. Therefore, it is possible to suppress the generation of deposits and achieve a high etching rate with a large amount of etchant. In the present invention, a relatively low pressure process, that is, the pressure in the processing chamber is several mTorr to 10
It is especially effective in the process of 0 mTorr. Of course C
Since O is not used, it is safe.

According to the etching method of claim 2, CH
With use of F ₃ gas / noble gas / O _2, 5mTorr~20mTorr the partial pressure of the CHF ₃ gas, CHF ₃ gas:
Since the etching is performed with the O ₂ ratio set to 1: 4 to 9,
As in the case of claim 1, CO is not used, deposition of deposits is small, and high-speed etching is possible. Moreover, CO
Since it does not use, it is highly safe.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross section of an etching apparatus 1 used for carrying out the etching method according to the present embodiment. A processing chamber 2 in this etching apparatus 1 is a hermetically sealed aluminum alumite-treated aluminum oxide. Is formed in a cylindrical processing container 3 made of, for example, and the processing container 3 itself is grounded through a ground wire 4. An insulating support plate 5 made of ceramic or the like is provided at the bottom of the processing chamber 2, and a substrate to be processed, for example, a semiconductor wafer (hereinafter referred to as “wafer”) W is placed on the insulating support plate 5. A substantially columnar susceptor 6 that constitutes a lower electrode for performing the above operation is housed so as to be vertically movable.

The susceptor 6 is supported by an elevating shaft 7 that freely penetrates through the insulating support plate 5 and the bottom of the processing container 3, and the elevating shaft 7 is a drive motor 8 installed outside the processing container 3. It can move up and down freely. Therefore, the operation of the drive motor 8 causes the susceptor 6 to move to the position shown in FIG.
As shown by the reciprocating arrow inside, it can move up and down. In order to ensure the airtightness of the processing chamber 2, a stretchable airtight member such as a bellows 9 is provided between the susceptor 6 and the insulating support plate 5 so as to surround the outside of the elevating shaft 7. There is.

The susceptor 6 is made of aluminum whose surface is oxidized, and has therein a temperature adjusting means, for example, a heating means (not shown) such as a ceramic heater, and an external coolant source (not shown). A coolant circulation path (not shown) for circulating a coolant between the two is provided, and the wafer W on the susceptor 6 can be maintained at a predetermined temperature. The temperature of the susceptor 6 is automatically controlled by a temperature sensor (not shown) and a temperature control mechanism (not shown).

An electrostatic chuck 11 for attracting and holding the wafer W is provided on the susceptor 6. As shown in FIG. 2, the electrostatic chuck 11 has a conductive thin film 1
2 has a structure in which it is sandwiched between polyimide resin 13 from above and below, and a voltage from a high voltage DC power source 14 installed outside the processing container 3, for example, a voltage of 1.5 kV to 2 kV is applied to the thin film 12. Then, the wafer W is attracted and held on the upper surface of the electrostatic chuck 11 by the Coulomb force generated at that time.

In the susceptor 6, as shown in FIG. 2, a supporting member for vertically moving in the susceptor 6 to lift up the wafer W from above the electrostatic chuck 11 to transfer the wafer W. A plurality of, for example, three lifter pins 20 functioning as are accommodated.

On the periphery of the susceptor 6, an inner focus ring 21 having a substantially annular plane is provided so as to surround the electrostatic chuck 11. The inner focus ring 21 is made of conductive single crystal silicon, and has a function of effectively injecting ions in plasma to the wafer W.

On the outer periphery of the inner focus ring 21, there is further provided an outer focus ring 22 having a substantially annular plane. The outer focus ring 22 is made of insulating quartz. The outer peripheral upper edge of the outer focus ring 22 is formed in a curved shape that is convex outward, and such a shape allows the gas to be smoothly discharged without settling. This outer focus ring 2
2 has a function of suppressing diffusion of plasma generated between the susceptor 6 and an upper electrode 51 described later, together with a shield ring 53 described later.

A baffle plate 23 made of, for example, an insulating material is disposed around the susceptor 6, and the inner peripheral portion of the baffle plate 23 is fixed by a fixing means such as a bolt via a quartz support body or the like. It is fixed to the susceptor 6.
Therefore, as the susceptor 6 moves up and down, the baffle plate 2
3 is also configured to move up and down. This baffle plate 23
A large number of through-holes 23a are formed in the inner surface of the inner wall 23c, and it has a function of uniformly discharging gas.

An insulating support material 3 is provided on the upper portion of the processing chamber 2.
1 and a cooling member 32 made of aluminum,
A diffusion member 33 for introducing an etching gas or another gas into the processing chamber 2 is provided. A cooling medium circulation path 34 is formed in the upper portion of the cooling member 32, and by circulating a chiller (refrigerant) supplied from the outside,
It has a function of cooling the upper electrode 51 described later to a predetermined temperature.

As shown in FIG. 2, the diffusing member 33 has a hollow structure having upper and lower two-stage baffle plates 35, and these upper and lower two-stage baffle plates 3 are provided.
A large number of diffusion holes 35a are formed in each of 5 so as not to overlap with each other in the vertical direction. A gas introducing port 36 is provided at the center of the diffusing member 33, and a gas introducing pipe 38 is connected via a valve 37. The valves 39, 40, 41 are provided in the gas introduction pipe 38.
Further, corresponding gas supply sources 45, 46, 47 are respectively connected via the mass flow controllers 42, 43, 44 for adjusting the flow rate.

Ar (argon) gas as a rare gas can be freely supplied from the gas supply source 45.
O ₂ (oxygen) gas can be supplied from 6 and C ₄ F ₈ gas can be supplied from the gas supply source 47.

The respective gases from the gas supply sources 45, 46 and 47 are supplied from the gas introduction pipe 38 to the introduction port 3
6. The diffusion member 33 is introduced into the processing chamber 2 through the diffusion hole 35a. On the lower surface of the cooling member 32, a cooling plate 50 having a large number of discharge ports 50a is formed.
2 are in close contact with each other, and as shown in FIG. 2, the gas in the baffle space S formed in the baffle plate 35 of the diffusion member 33 is uniformly discharged downward.

An upper electrode 51 is fixed to the lower surface of the cooling plate 50 so as to face the susceptor 6. The upper electrode 51 is made of conductive single crystal silicon, is fixed to the peripheral portion of the lower surface of the cooling plate 50 by a bolt (not shown), and is electrically connected to the cooling plate 50. The upper electrode 51 also has a large number of ejection ports 51a.
And the discharge port 50 of the cooling plate 50 is formed.
a. Therefore, the gas in the baffle space S is uniformly discharged to the wafer W on the electrostatic chuck 11 through the discharge port 50a and the discharge port 51a of the upper electrode 51.

A shield ring 53 is arranged at the peripheral portion of the lower surface of the upper electrode 51 so as to cover the aforementioned fixing bolts (not shown). This shield ring 53
Is made of quartz, and has a function of forming a gap narrower than the gap between the electrostatic chuck 11 and the upper electrode 51 with the outer focus ring 22 and suppressing diffusion of plasma. An insulating ring 54 made of fluorine-based synthetic resin is provided between the upper end of the shield ring 53 and the ceiling wall of the processing container 3.

A pressure sensor 55 for detecting the degree of vacuum in the processing container 3 is mounted on the side surface of the processing container 3. The detection signal of the degree of vacuum detected by the pressure sensor 55 is input to the controller 74 described later, and the degree of vacuum in the processing container 3 is constantly monitored.

On the other hand, an exhaust pipe 62 communicating with a vacuuming means 61 such as a vacuum pump is connected to the lower portion of the processing container 3, and the above-mentioned baffle plate 2 arranged around the susceptor 6 is connected.
The inside of the processing chamber 2 is several mTorr to 10
Evacuate to any vacuum up to 0 mTorr,
It is possible to maintain this.

Next, the high frequency power supply system of the etching apparatus 1 will be described. First, for the susceptor 6 serving as the lower electrode, the frequency is about several hundred kHz, for example, 80.
The power from the high frequency power source 63 that outputs the high frequency power of 0 kHz is supplied through the matching device 64. On the other hand, to the upper electrode 51, the power from the high frequency power source 66 that outputs the high frequency power of a frequency of 1 MHz or higher, for example, 27.12 MHz, which is higher than that of the high frequency power source 63, via the matching unit 65, is described above. Cooling member 3
2. It is configured to be supplied through the cooling plate 50.

A load lock chamber 72 is adjacent to a side portion of the processing container 3 via a gate valve 71. In the load lock chamber 72, a wafer W that is a substrate to be processed is provided.
A transfer means 73 such as a transfer arm is provided for transferring the liquid crystal to and from the processing chamber 2 in the processing container 3.

Next, the control system of the etching apparatus 1 will be described. A drive motor 8 for moving the susceptor 6 up and down, a high voltage DC power supply 14, and a lifter pin 2 in the susceptor 6.
0, valves 39, 40, 41, mass flow controllers 42, 43, 44, evacuation means 61, high frequency power supply 6
3, 66 are controlled by the controller 74, respectively.

The main part of the etching apparatus 1 for carrying out the etching method according to the present embodiment is configured as described above, and an oxide film (SiO ₂ ) of, for example, a silicon wafer W is controlled under the control of the controller 74. The operation and the like in the case of performing the etching process will be described first. First, after the gate valve 71 is opened, the transport means 7 is opened.
The wafer W is loaded into the processing chamber 2 by 3. At this time, due to the operation of the drive motor 8, the susceptor 6 descends, and the lifter pin 20 is in a standby state for receiving the wafer W protruding onto the electrostatic chuck 11. Then, the wafer W carried into the processing chamber 2 by the carrying means 73 is transferred onto the lifter pin 20 protruding above the electrostatic chuck 11.
After transferring the wafer W onto the lifter pin 20 in this manner, the transfer means 73 is retracted and the gate valve 71 is closed.

On the other hand, when the transfer of the wafer W onto the lifter pins 20 is completed, the drive motor 8 is operated to move the susceptor 6 to a predetermined processing position, for example, when the gap between the upper electrode 51 and the susceptor 6 is 10 mm to 20 mm. The lifter pins 20 supporting the wafer W are lowered into the susceptor 6 at the same time. Thus, as shown in FIG. 2, the wafer W is placed on the electrostatic chuck 11. Then, a predetermined voltage is applied from the high-voltage DC power supply 14 to the conductive thin film 12 in the electrostatic chuck 11, and the wafer W is attracted and held on the electrostatic chuck 11.

Then, the inside of the processing chamber 2 is evacuated by the evacuation means 61 to reach a predetermined degree of vacuum (pressure reduction degree), and then the gas required for the etching process is supplied from the gas supply sources 45, 46 and 47. It is supplied at a predetermined flow rate, and the pressure in the processing chamber 2 is set and maintained at a predetermined degree of vacuum, for example, 40 mTorr.

Next, a high frequency power source 6 is applied to the upper electrode 51.
6 to 27.12MHz in frequency, power is 2k
When the high frequency power of W is supplied, plasma is generated between the upper electrode 51 and the susceptor 6. At the same time, the frequency of the susceptor 6 is 800 k from the high frequency power source 64.
A high frequency power having a frequency of Hz and a power of, for example, 1 kW is supplied.

Then, the processing chamber 2 is generated by the generated plasma.
The process gas inside is dissociated, and the etchant ions generated at that time are incident on the silicon oxide film (SiO ₂ ) on the surface of the wafer W while the incident speed of the etchant ions is controlled by the high frequency of a relatively low frequency supplied to the susceptor 6. Will be etched.

In this case, in this embodiment, the processing gas used in the etching process is C ₄ F ₈ gas, A
An r (argon) gas and O ₂ (oxygen) are introduced into the processing chamber 2, and the pressure inside the processing chamber 2 is set to 40 mTorr. The partial pressure of C ₄ F ₈ gas is 0.5 mTorr to 1.
The flow rate of Ar (argon) gas is appropriately set so as to be 5 mTorr. Further, the amount of O ₂ (oxygen) is set to be 1.5 to 5 times that of the C ₄ F ₈ gas.

By setting each of these gases, the processing container 3
The deposit deposited on the inner wall of the can be suppressed to a low level, and a high etching rate can be obtained. Further, unlike the conventional etching method in which C ₄ F ₈ gas that generates an etchant species and CO (carbon monoxide) are used together, in the etching method according to the present embodiment, CO is not used, so safety is also improved. doing.

In the etching process, C ₄ F ₈ was used as a gas for generating the etchant species, but CHF ₃ gas was used instead of C ₄ F ₈ and the partial pressure was 5 mTorr.
rF to 20 mTorr and CHF ₃ gas:
Even when etching is performed with the O ₂ ratio set to 1: 4 to 9, the deposit attached to the inner wall of the processing container 3 can be suppressed to a low level, and a high etching rate can be obtained. Of course, since CO is not used, it is safe in terms of work.

[0041]

【Example】

(First Example) Etching apparatus 1 used in the above embodiment
Using a mixed gas of C ₄ F ₈ gas / Ar (argon) gas / O _{2 as} the gas used in the etching process, the etching rate and the exhaust rate when the flow rate of the C ₄ F ₈ gas was changed The ion analysis result (number of ions by Q-Mass) in the graph is shown in the graph of FIG. The process pressure in the processing chamber 2 was maintained at 40 mTorr, and Ar (argon) was used.
Gas flow rate is 560 sccm, O ₂ flow rate is 3 sccm
The flow rate of C ₄ F ₈ gas was changed. The temperature is 20 ° C. in the lower part of the processing chamber 2, 30 ° C. in the upper part, and the temperature of the wafer W having a diameter of 6 inches, which is the target substrate, is 40 ° C. Regarding the high frequency power, a frequency of 27.12 MHz and 2000 W of high frequency power is applied to the upper electrode 51.
On the other hand, the susceptor 6 serving as the lower electrode has a frequency of 0.
A high frequency power of 900 W was applied at 8 MHz.

According to the graph of FIG. 3, the flow rate of the C ₄ F ₈ gas is between 10 sccm and 15 sccm, that is, when converted by the partial pressure ratio, 10 / (560 + 3 + 10) -15 / (5
60 + 3 + 15) That is, it can be confirmed that a high etching rate of about 650 nm / min is obtained in the range of 0.017 to 0.026, or 0.69 mTorr to 1.04 mTorr in terms of partial pressure.

Further, the number of CF ₃ ⁺ ions as the etchant species is always larger than the number of CF ⁺ ions as the depot species, and CF ₃ ⁺ / CF ⁺ has a C ₄ F ₈ gas flow rate of 10.
1.74 when the sccm, flow rate of C ₄ F ₈ gas is 20s
A high value of 1.38 is obtained even at ccm. Therefore, etching in which the number of etchant species is greater than that of depot species, the amount of deposits is small, and a high etching rate can be obtained can be performed on the silicon oxide-based material layer on the wafer W.

(Second Example) On the other hand, this time, using the etching apparatus 1 used in the above-mentioned embodiment, the gas used in the etching process is C ₄ F ₈ gas / Ar (argon) gas /
Using a mixed gas of O _2, when changing the flow rate of O _2, 4 ion analysis in the exhaust and the etching rate
Is shown in the graph. The process pressure in the processing chamber 2 is 40m.
Maintained at Torr, Ar (argon) gas flow rate is 56
The flow rate of 0 sccm and the C ₄ F ₈ gas were fixed at 10 sccm. Other conditions are the same as those in the first embodiment.

According to this, the flow rate of O ₂ is ₂ sccm to
When converted between 3 sccm, that is, the ratio with C ₄ F ₈ gas,
C ₄ F ₈ gas: O ₂ = 3.3 to 5 and approximately 650 nm
It can be confirmed that a high etching rate of / min average is obtained. Also, CF ₃ ⁺ / CF ⁺ is 1.58 to
Since it is 1.95, it can be confirmed that the etching with a small deposition amount and a high etching rate can be performed on the silicon oxide based material layer on the wafer W.

[0046]

According to the etching method of the first and second aspects, since CO is not used, the safety is improved as compared with the conventional etching process in which CO is added. Moreover, since the ratio of CF ₃ ions as an etchant to CF ions as a depot species is properly controlled by O ₂ ,
In addition to suppressing the generation of deposits, a high etching rate equal to or higher than that of the conventional process in which CO is added can be obtained. Therefore, the cleaning cycle in the chamber of the processing apparatus can be made longer than before and the throughput can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory diagram of an etching apparatus used in an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a main part near an upper electrode in the etching apparatus of FIG.

FIG. 3 is a graph showing the etching rate and the ion analysis result in the exhaust gas when the flow rate of C ₄ F ₈ gas was changed by the etching method performed according to the example of the present invention.

FIG. 4 is a graph showing the etching rate and the ion analysis result in the exhaust gas when the flow rate of O ₂ was changed by the etching method performed according to the example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Etching apparatus 2 Processing chamber 3 Processing container 6 Susceptor 11 Electrostatic chuck 45, 46, 47 Gas supply source 51 Upper electrode 61 Vacuum drawing means 63, 66 High frequency power supply W Wafer

Claims (2)

[Claims] 1. A silicon oxide-based material layer on a substrate to be processed in a processing chamber in which a predetermined processing gas is introduced and a plasma is generated in the processing chamber under a predetermined degree of reduced pressure. C ₄ F ₈ gas, a rare gas, and O ₂ are used as a processing gas, and C ₄ F ₈
The partial pressure for the process pressure of gas is 0.5 mTorr
1.5 mTorr, C ₄ F ₈ gas: O ₂ ratio of 1: 1.5
An etching method, characterized in that the etching is performed by setting it to -5. 2. A silicon oxide-based material layer on a substrate to be processed in a processing chamber, wherein a predetermined processing gas is introduced into the processing chamber and the plasma is generated under the predetermined pressure reduction degree. CHF ₃ gas, a rare gas, and O ₂ are used as a processing gas.
Partial pressure for ₃ gas process pressure is 5 mTorr to 20
An etching method, characterized in that the etching is performed by setting the ratio of mTorr and CHF ₃ gas: O ₂ to 1: 4 to 9.